U.S. patent number 4,316,598 [Application Number 06/172,399] was granted by the patent office on 1982-02-23 for balanced relief valve with novel seal.
This patent grant is currently assigned to Vapor Corporation. Invention is credited to Robert L. Maggio.
United States Patent |
4,316,598 |
Maggio |
February 23, 1982 |
Balanced relief valve with novel seal
Abstract
A pilot operated pressure relief valve for use on medium and
high pressure vessels, conduits, and the like. A two-stage,
non-flowing pilot valve operates a main relief valve of
substantially greater capacity. In a preferred embodiment the main
valve is mounted directly onto the pressure vessel which is to be
vented at a predetermined pressure. The pilot is preferably mounted
closely adjacent to the main valve for operating communication
therewith. An improved main valve seal is provided which allows the
use of commonly available seal configurations in a simple and
easily assembled construction to provide a fast operating, high
pressure seal.
Inventors: |
Maggio; Robert L. (Elmhurst,
IL) |
Assignee: |
Vapor Corporation (Chicago,
IL)
|
Family
ID: |
22627552 |
Appl.
No.: |
06/172,399 |
Filed: |
July 25, 1980 |
Current U.S.
Class: |
251/63; 251/361;
137/492; 251/364 |
Current CPC
Class: |
F16K
17/105 (20130101); Y10T 137/7769 (20150401) |
Current International
Class: |
F16K
17/10 (20060101); F16K 17/04 (20060101); F16K
031/122 () |
Field of
Search: |
;137/488,489,492,492.5
;251/361,362,DIG.1,360,364 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
714339 |
|
Jul 1965 |
|
CA |
|
983178 |
|
Feb 1965 |
|
GB |
|
Primary Examiner: Cohan; Alan
Attorney, Agent or Firm: Lidd; Francis J.
Claims
I claim:
1. A pilot operated pressure relief valve having a housing, a
reciprocating shut-off member in said housing defining first and
second pressurized volumes above and below the shut-off member,
respectively, comprising;
a first aperture communicating with said first volume;
second aperture communicating with said second volume, and defining
an orifice;
an orifice insert concentric with said orifice, and an orifice seat
secured to said housing, said orifice insert mounted on said
orifice seat, said orifice insert and said orifice seat defining
first and second sides, respectively, of a seal retention
groove;
said orifice insert and said orifice seat defining a planar surface
facing said shut-off member;
a seal in said goove, said seal and said groove defining a valve
seat for said shut-off member;
a first plurality of apertures communicating with said first side
of said seal retention groove in spaced relationship in the
periphery of said orifice insert, said first plurality of apertures
terminating in said planar surface and communicating with said
second volume;
a second plurality of apertures communicating with the second side
of said seal retention groove in spaced relation in the periphery
of said orifice seat, said second plurality of apertures
terminating in said planar surface and communicating with said
second volume;
means seating said seal on said closure member;
means maintaining said closure member in sealing engagement with
said seal for equal pressure in said volumes; and
means selectively venting said first volume, wherein said product
pressure displaces said shut-off member from said seat, and
increased pressure in said seal groove beneath said seal caused by
product flow through said orifice is relieved by said
apertures.
2. The valve claimed in claim 1 wherein said orifice insert is
removable.
3. The valve claimed in claim 1 wherein said seal retention groove
is asymmetrical.
4. The valve claimed in claim 1 wherein said seal retention groove
is triangular.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to pressure operated relief valves
and more particularly concerns a novel pressure seal for a balanced
pressure relief valve. In particular, the seal disclosed provides
improved relief valve operation by preventing simmering of the
valve and leakage.
Heretofore it has been difficult if not impossible to utilize
conventional seals such as "O" rings in piston shut-off valve
constructions where one end of the closure member and seat are in
abutting relationship. With this type of "face" seal, in high
pressure service, rapid movement of the closure member away from
the seat results in a 90.degree. change in vented product flow
subjecting the seal to substantial aerodynamic forces. These forces
tend to lift the seal from its retaining groove resulting in either
damage to the seal and impaired subsequent operation, or complete
removal of the seal and failure of the valve. These forces also
impinge abrasive particles against the seal resulting in damage to
and eventual destruction of the seal.
Conventional solutions to seal retention under these conditions
usually involve use of seals having cross-sections which can be
mechanically retained by positive locking devices such as screws,
rivets, or other means. These valves, therefore, in addition to
requiring specially manufactured seals are somewhat dificult to
maintain since seal replacement has become complex.
The method of main or relief valve seal retention disclosed in this
application allows the use of a commonly available "O" ring in a
configuration which effectively eliminates the aerodynamic forces
tending to lift the "O" ring from its sealing position during valve
operation.
Prior art relief and/or valve combinations are disclosed in U.S.
Pat. Nos. 3,595,263, 3,664,362, 3,512,560 and 3,568,706; however,
prior art attempts at using face seals between the piston and the
sealing seat in these valves have not been successful due to
removal of the seal material by the turbulence of the fluid flow
during valve operation. This deterioration or destruction of the
seal results in leakage and valve simmering.
Accordingly, in order to prolong the service life of valves
employed to relieve excess pressure in large, high pressure
vessels, it is desirable to provide a sealing member that is not
subject to abrasion from the flowing media and is not custom
molded.
SUMMARY OF THE INVENTION
A pilot operated pressure relief valve is described that employs
mechanically independent first and second pressure operated stages.
In a preferred embodiment, the two-stage pilot valve operates a
substantially larger main valve by venting the main valve head
volume. The design of the main valve closure is in pressure
equilibrium with the tank or pressure vessel; however, when the
head volume is vented to atmosphere, the tank pressure is utilized
to open the main valve providing the desired pressure relief. An
additional signal to the pilot valve is provided by a down stream
venturi or ram tube which provides an indication of true tank
pressure allowing the pilot and main valve to reset at a correct
tank pressure independent of the magnitude of main valve flow. A
remote pressure pick up may also be employed.
A feature of the two-stage pilot valve disclosed utilizes a
specific storage volume to control the rate of change of actuating
product flow, to be vented by the main valve, between the first and
second stages and is disclosed more completely in United States
patent application Ser. No. 943,377, filed Sept. 18, 1978,
incorporated by reference herein. These controlled rates of
operation provide positive and more accurate relief and blowdown
operations of both the pilot and main valve.
A main or relief valve seal defined in the seat of the main valve
is also disclosed that utilizes vent apertures in predetermined
locations adjacent to a seal retention groove, providing effective
relief of pressure differentials and resistance to aerodynamic
forces acting on the seal at the time of valve operation. This
allows utilizing commonly available seals which can easily be
replaced resulting in substantially reduced cost and effort of
valve maintenance. Also, the probability of malfunction of the main
or pressure relief valve is greatly reduced. A further technical
description can be obtained by review of the bulletin included
herewith as an Appendix.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent
when reading the following detailed description upon reference to
the drawings, in which:
FIG. 1 is a semi-pictorial view of a pilot operated relief valve in
a preferred but not exclusive embodiment, wherein the two-stage
pilot valve is mounted closely adjacent to the main valve;
FIG. 2 is a sectional view of the main valve portion of the
invention in the valve open position including the novel seal and
pilot valve connecting tube;
FIG. 3 is a view taken along line 3--3 in FIG. 2;
FIG. 4 is a detailed cross-section of the novel main valve seal of
the invention showing the features of seal retention in the
cross-section.
While the invention will be described in connection with a
preferred seal and retention groove, it should be understood that
it is not intended to limit the invention to the configuration
disclosed. On the contrary, it is intended to cover all
alternatives, modifications, and equivalances which may be included
within the spirit and scope of the invention and as defined by the
appended claims.
DETAILED DESCRIPTION OF THE INVENTION
In reference to FIGS. 1 and 2, the pressure operated relief valve
20 disclosed herein consists of a pilot valve generally shown as 5
(re. FIG. 1), having a first stage 10 and a second stage generally
shown as 41 contained in a body 14. In a preferred embodiment the
pilot is mounted closely adjacent to the upper end of a main valve
7 communicating with the pilot 5 through main valve port 61 and
port 11 of the pilot valve 5. In the disclosed embodiment a pipe or
conduit 9 connects 61 and 11. Additionally, there is an
inner-connecting external pressure tube 6 further communicating
with a pressure tap 63 contained in the lower portion of the main
valve 7 just above the main valve inlet flange 66 and inlet port
65. The pressure tap 63 communicates with a total pressure pilot
ram tube 64, providing a tank pressure signal during main valve
flow. Typically, the lower flange 66 of the main valve communicates
with a pressure vessel, or conduit. Operation of the pressure
operated relief valve therefore vents the product contained in the
above mentioned pressure vessel or conduit.
In operation, assuming that tank pressure is below the relief
setting of valve 20, as shown in FIGS. 1 and 2, static pressure
from the associated vessel or conduit is applied to the main valve
piston through the port 65 and the pilot valve through port 12 and
tube 6, as discussed above. Pressure is therefore communicated
internal to the pilot valve to the first 10 and second stage 41
elements.
The design of the pilot valve 5 and the stages 10 and 41 is best
described in United States Patent application Ser. No. 943,377
mentioned previously. Accordingly, a detailed description will not
be herein provided and the emphasis will be in describing the main
valve and the seal assembly.
Tank pressure is sensed through the main valve inlet 65, and the
pressure setting of the pilot valve first stage is determined by
the force preload of a compression spring contained in the pilot
valve first stage setting the first 10 and second 41 stages of the
pilot valve 5 into operation.
After operation of the first 10 and second 41 stages, total
pressure of the vented tank or conduit is now supplied to the ram
or pilot tube 64 located in the relief inlet at 63, and
communicates this pressure through the tube 6 and port 12, thereby
maintaining the second stage pilot 41 in a depressed or relief
position.
Returning now to the main or relief valve 7; operation of the novel
seal retention device during the relief action initiated by the
operation of first and second stages, 10 and 41, of the relief
valve disclosed will be described.
As stated above, when the two pilot stages 10 and 41 are in a flow
configuration shown and the main valve inlet 65 communicates with a
vessel or conduit to be relieved, product pressure enters the main
valve through the inlet 65 and is exerted through product transfer
to the lower portion of the main valve piston 69 and acts through
port 71 on main valve lower piston active area 75. Similarly,
product pressure is transmitted via port 63, tube 6, inlet port 12,
and pilot internal ports to the pilot valve port 11 which, in turn,
communicates with main valve inlet port 61 to apply product
pressure to the main valve head volume 68 and associated main valve
upper head area 74. Since area 74 is greater than 75, the relief
valve is held in the closed position compressing the main valve
seal 103 that may, in the preferred embodiment, be an O-ring.
On operation of the pilot valve 5 providing product flow, the main
valve head volume 68 is vented to the atmosphere via the flow path
61, 11, and the pilot internal ports exiting through second stage
port.
As a consequence of the venting of main valve head volume 68,
piston 69 rises rapidly and product flow passes through the main
valve orifice 71 and main valve exit 67.
At this point product flow through 71, is directed against the
lower face 75 of the piston 69 and then radially when passing
through the main valve cylinder port 117, and redirected to exit
the main valve exit port 67.
The turbulence produced by this flow includes a substantial vortex
formation adjacent to the seal 103 (re. FIG. 4) partially retained
in a generally triangular groove defined by an orifice seat 100 and
orifice insert 101. The orifice insert 101 is removably mounted in
the main valve 7 by threads or other means and may be removed for
servicing or replaced with a different size insert to change the
flow capacity of the main valve 7. The groove is asymmetric in
cross section with a cavity 115 on the inside diameter side larger
than a cavity 116 on the outside diameter side to allow for thermal
expansion of the seal 103. The groove is of a size, however, to
extrude the seal 103 outward to engage the piston 69 in the valve
closed position. Under these conditions the low pressures produced
by the above mentioned vortices would result in the gases trapped
in a seal cavity 116 defined within the triangular groove and
around the seal 103, forcing the seal 103 out of the triangular
seal cavity or groove past the orifice seat and insert 100 and 101.
Utilization of a plurality of vent apertures 109, as shown,
however, adjacent to both the orifice seat 100 and insert 101,
allow the gas from the cavities 115 and 116 to vent, thereby
eliminating the tendency to dislodge the seal member 103. In this
manner, a relatively simple and easy to manufacture seal, such as
an "O" ring can be used. In addition, through the employment of the
disclosed construction the seal member 103 is out of the flow
direction thereby avoiding direct impingement by abrasive
particles.
The seal construction described above has been found to be highly
effective in valves having piston 69 diameters as large as 8 inches
and pressures as high as 2220 pounds per square inch. The method
allows the relatively simple construction complying at the most
tool removable components to provide a reliable and lasting seal
for a large capacity relief valve, since the seal 103 is positioned
out of the turbulence of the flow of the product while still
insuring an efficient seal.
Thus, it is apparent that there has been provided in accordance
with the invention a pilot operated relief valve utilizing a
two-stage non-flow pilot and improved main valve which fully
satisfies the objects, aims and advantages set forth above.
While the invention has been described in connection with specific
configuration and component embodiments, it is evident that many
alternatives, modifications, and variations will be apparent to
those skilled in the art in light of the foregoing description.
Accordingly, it is intended to embrace all such alternatives,
modifications, and variations as fall within the spirit and scope
of the following claims.
* * * * *